Vulcanization process with s,s&#39;-carbonyl-bis-dialkyldithiophosphate

ABSTRACT

A PROCESS FOR THE VULCANIZATION OF TERPOLYMERS OF ETHYLENE AND PROPYLENE, ALSO KNOWN AS EPDM RUBBERS, IS DESCRIBED. MORE PARTICULARLY VULCANIZATION ACCELERATORS FOR SUCH A PROCESS HAVING THE FORMULA   (R-O)2-P(=S)-S-CO-S-P(=S)(-O-R)2   IN WHICH THE RADICALS R REPRESENT THE SAME OR DIFFERENT STRAIGHT CHAINED OR BRANCHED LOWER ALKYL RADICALS, EACH OF WHICH MAY BE SUBSTITUTED BY A LOWER ALKOXY GROUP, ARE DESCRIBED.

United States Patent Office 3,778,419 Patented Dec. 11, 1973 3,778,419 VULCANIZATION PROCESS WITH S,S'-CARBONYL- BIS-DIALKYLDITHIOPHOSPHATE Rudiger Schubart, Ulrich Eholzer, Theo Kempermann, and Ernst Roos, Cologne, Germany, assignors to Bayer Aktiengesellschaft, Leverkusen, Germany Not Drawing. Original application Dec. 21, 1970, Ser. No. 100,361, now Patent No. 3,697,433. Divided and this application Feb. 2, 1972, Ser. No. 222,978 Claims priority, application Germany, Jan. 13, 1970, P 20 01 151.2 Int. Cl. C08d 9/00, 13/28; C08f 27/06 U.S. CL 260-795 B Claims ABSTRACT OF THE DISCLOSURE A process for the vulcanization of terpolymers of ethylene and propylene, also known as EPDM rubbers, is described. More particularly vulcanization accelerators for such a process having the formula R0 OR in which the radicals R represent the same or different straight chained or branched lower alkyl radicals, each of which may be substituted by a lower alkoxy group, are described.

CROSS-REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 100,361 filed Dec. 21, 1970 and now US. Pat. 3,697,433.

The present invention relates to a process for the vulcanization of terpolymers of ethylene and propylene, also known as EPDM rubbers, and more particularly to vulcanization accelerators for such a process.

As is well known, EPDM rubbers can be vulcanized with sulphur in the presence of an accelerator system which contains a conventional primary accelerator, e.g. one taken from the group of thiazole accelerators (see S. Bostrtim, Kautschuk-Handbuch, volume 4, Stuttgart, 1961, pages 300-307) and as additional accelerators those taken from the group of thiuram and dithiocarbamate accelerators (see S. Bostrom, Kautschuk-Handbuch, Stuttgart, 1961, volume 4, pages 307-316) and optionally additional thioureas (see Technical Information Leaflet No. 20 of Farbenfabriken Bayer AG, published Jan. 2, 1969, Order No. KA 4519). Without the addition of dithiocarbamate accelerators, the aforesaid accelerator systems only reach vulcanization rates which are too slow for technical purposes. Although the addition of dithiocarbamate accelerators, such as zinc dimethyldithiocarbamate or zinc diethyl dithiocarbamate increases the vulcanization rate, it entails the serious disadvantage that these accelerator systems in many cases cause the formation of unwanted surface deposits (bloorn on the surfaces of the vulcanizates (see Ullmanns Encyklopadie der technischen Chemie, 3rd Edition, publishers, Urban and Schwarzenberg, Munich, Berlin, 1957, volume 9, page 370).

In practice, the rate of vulcanization can only be increased to a very limited extent by increasing the amount of dithiocarbamate because larger amounts reduce the stability of the mixtures to such an extent that the process becomes unreliable (see Technical Information Leaflet N0. 20 of Farbenfabn'ken Bayer AG, published I an. 2, 1969, Order No. 4519).

The same applies to the addition of thioureas.

It has now been found that these disadvantages no longer occur in the vulcanization of ethylene propylene terpolymers in the presence of sulphur or sulphur donors and vulcanization accelerators if one uses as vulcanization accelerators S,S-carbonyl-bis-dialkyl dithiophosphates of the general formula in which the radicals R denote the same or different straight chained or branched lower alkyl radicals each of which maybe substituted by a lower alkoxy' group,

with the addition of a conventional thiazole accelerator and, if desired, also a compound taken from the group of thiuram or dithiocarbamate accelerators and/ or optionally a thiourea. The lower alkyl radicals may have up to 6 carbon atoms and preferably have 1 to 4 carbon atoms. The lower alkoxy radicals mentioned above as substituents may have 1 to 4 and preferably have 1 to 3 C atoms. A lower alkyl radical R substituted with a lower alkoxy group may have a total of up to 10 carbon atoms.

The following are examples of radicals R in Formula I: Methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, tertiary butyl, n-pentyl, 3-methylbutyl, 2- methylbutyl, Z-pentyl, S-pentyl, 3-methyl-2-buty1, 2-methyl-2-butyl, 2,2-dimethylpropyl, n-hexyl, 2-hexyl, 3-l1exyl, 4-methylpentyl, S-methylpentyl, Z-methylpentyl, 4-methyl- 2-pentyl, 3-methyl-2pentyl,3-methyl-3-pentyl, 3-methyl-2- pentyl, 3,3-dimethylbutyl, 3,3-dimethyl-2-butyl, 2,2-dimethylbutyl, 2-methyl-3-pentyl, 2-ethylbutyl, Z-methyl-Z- pentyl, 2,3-dimethylbutyl, 2,3-dimethyl-2-butyl, 2-methoxyethyl, Z-ethoxyethyl, 2-propoxyethyl, 2-isopropoxyethyl, 2-, ethoxypropyl, 2-ethoxypropyl, 2-propoxypropyl and 2-isopropoxypropyl.

The following are mentioned as examples of S,S-carbonyl-bis-dialkyldithiophosphates which may be used in accordance with the invention:

S,S'-carbonyl-bis-dimethyl-dithiophosphate, S,S'-carbonyl-bis-diethyl-dithiophosphate, S,S-carbonyl-bisdi-n-propyl-dithiophosphate, S,S-carbonyl-bis-di-isopropyl-dithiophosphate, S,S'-carbonyl-bis-di-n-butyl-dithiophosphate, S,S-carbonyl-bis-diisobutyl-dithiophosphate, S,S-carbonyl-bis-di-sec.-butyl-dithiophosphate, S,S'-carbonyl-bis-ditert.-butyl-dithiophosphate, S,S'-carbonyl-bis-di-n-pentyl-dithiophosphate, S,S-carbonyl-bis-di-2-methylbutyl-dithiophosphate, S,S-carbonyl-bis-di-Z-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-3-pentyl-dithiophosphate, S,S-carbonyl-bis-di-3-methyl-2-butyl-dithiophosphate, S,S'-carbonyl-bis-di-Z-methyl-2-butyl-dithiophosphate, S,S'-carbonyl-bis-di-n-hexyl-dithiophosphate, S,S-carbonyl-bis-di-Zhexyl-dithiophosphate, S,S'-carbonyl-bis-di-3-hexyl-dithiophosphate, S,S'-carbonyl-bis-di-4-methyl-pentyl-dithiophosphate, S,S-carbonyl-bis-di-Z-methylpentyl-dithiophosphate, S,S'-carbonyl-bis-cli-2-methyl-2-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-3,3-dimethyl-butyl-dithiophosphate, S,S-carbonyl-bis-di-2,2-dimethylbutyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methyl-3-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-3ethylbutyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methyl-pentyl-dithiophosphate, S,S'-carbonyl-bis-di-2,3-dimethyl-butyl-dithiophosphate, S,S-carbonyl-bis-di-2-methoxyethyl-dithiophosphate, S,S-carbonyl-bis-di-Z-ethoxyethyl-dithiophosphate, S,S'-carbonyl-bis-di-2-propoxyethyl-dithiophosphate, S,S-carbonyl-bis-di-2-isopropoxyethyl-dithiophosphate, S,S'-carbonyl-bis-di-2-methoxypropyl-dithiophosphate, S,S-carbonyl-bis-di-2-ethoxypropyl-dithiophosphate, S,S'-Zarbonyhbis-di2-isO-prop0xypropyl-dithiophosphate an S,S'-carbonyl-bis-di-Z-propoxypropyl-dithiophosphate.

One may, of course, also use S,S'-carb'onyl-b1sialkyldithiophosphates of Formula I which have been obtained from alcoholic mixtures, e.g. isomeric mixtures such as a mixture of various isomeric butanols or pentanols or commercial alcoholic mixtures containing alcohols with different numbers of carbon atoms. these mixtures consequently having various radicals R (Formula I). V

The vulcanization accelerators preferably used are S,S'- carbonyl-bis-di-n-butyl-dithiophosphate and S,S'-carbonylbis-isobutyl-dithiophosphate.

The accelerator systems according to the invention in addition contain an accelerator from the group of thiazole accelerators, for example Z-mercaptobenzothiazole, dibenzothiazyl disulphide or the zinc salt of Z-mercaptobenzothiazole.

Additional accelerators taken from the group of thiuram and dithiocarbamate accelerators may also be used, e.g. tetramethylthiuram disulphide, tetraethylthiuram disulphide, tetramethylthiuram monosulphide, dimethyldiphenyl thiuram disulphide and/or thioureas such as diphenyl thiourea, ethylene thiourea, N,N'-dimethylthiourea, N,N'- diethylthiourea, N,N'-dibutylthiourea and thiourea itself.

The individual components of the accelerator system may advantageously be used in the amounts indicated below (in parts by weight based on 100.0 parts by weight of EPDM rubber):

S,S'-carbonyl-bis-dialkyl-dithiophosphate-approximately 0.1 to approximately 5.0 v

mercapto accelerator-approximately 0.2 to approximately thiuram or dithiocarbamate accelerator to approximately 2.0

thiourea0 to approximately 2.0.

The quantity of sulphur to be used is about 0.2 to about 3.5 parts by weight based on 100.0 parts by weight of EPDM rubber, preferably 1.0 to 2.0 parts by weight. Sulphur donors such as N,N-dithio-bis-morpholine, dipentamethylene thiuram tetrasulphide, N,N'-dithio-bishexahydro-2H-azepinone- (2) and 2-benzothiazyl-dithio- N-morpholide may also be used in quantities corresponding to the required amount of sulphur indicated.

The individual components of the accelerator system may be added to the EPDM rubbers or rubber mixtures before vulcanization either separately or in the form of a mixture or a preliminary mixture of rubber and accelerator (see Ullmanns 'Encyklopadie der technischen Chemie, 3rd Edition, publishers Urban und Schwarzenberg, Munich, Berlin, 1957, volume 9, page 364.

The EPDM rubbers may contain all the usual additives such as fillers, especially carbon blacks, mineral oils, plasticizers, tackifiers, accelerator activators, especially stearic acid, waxes, anti-oxidants, substances which protect against ozone, blowing agents, dyes or pigments.

Vulcanization of EPDM rubbers is generally carried out at temperatures of between about 120 C. and about 300 C., using any of the usual vulcanization processes employed in industry such as press heating, heating with In addition 'to the commercial pure alcohols, one inay also usemixtures of alcohols ROI-I. Both isomeric mixtures, for example mixtures of n-propanol and isopropanol or of n-butanol and isobutanol or the isomeric mixture of various pentyl alcohols and mixtures of alcohols with different numbers of C atoms, e.g. a mixture of 50% by weight of n-butanol and 50% by weight of n-pentanol may be used. One may, of course, also use commercial alcohol mixtures as well as mixtures which contain numerous individual alcohols of different chemical constitutions.

The reaction of phosphorus pentasulphide with alcohol or alcohol mixtures is carried out under normal or elevated pressure in a temperature range of 10 C. to 100 0., preferably at 30 C. to 50 C. and normal pressure. The reactants are advantageously put into'the process in equimolar quantities although an excess or subequivalent amount of phosphorus pentasulphide may, of course, be used. Furthermore, phosphorus pentasulphide may be put into the reaction with the corresponding alcohol or alcohol mixture diluted with an inert organic solvent such as cyclohexane, benzene, toluene, xylene or diethylether, diisopropylether, tetrahydrofuran or dioxane. Alternatively, phosphorus pentasulphide may, of course, be suspended in one of the above-mentioned solvents and reacted in this form with the corresponding alcohol or alcohol mixture. It will generally be preferable to introduce the dry phosphorus pentasulphide into the reaction vessel and slowly add the undiluted alcohol or alcohol mixture. The dialkyl or dialkoxyethyldithiophosphoric acids obtained in this way are liquid compounds. For subsequent reactions, neutralization of the corresponding dithiophosphoric acid with ammonia or an amine such as triethylamine or pyridine may be carried out in another solvent such as diethylether, diisopropylether, dioxane, tetrahydrofuran, benzene, toluene or xylene but preferably, neutralization of dithiophosphoric acid is carried out in water, using an amine such as triethylamine or ammonia but more simply still with aqueous alkali metal hydroxide solutions such as sodium hydroxide or potassium hydroxide solution at room temperature. The salt solutions prepared in this way can now be directly converted into the corresponding S,S'-carbonyl-bis-dialkyl-. or S,S-carbonyl-bis-dialkoxyethyl-dithiophosphates by means of phosgene. The phosgenation reaction may be carried out in a temperature range of 20 C. to 100 C., preferably between -5 C. and 10 C., and the reactants may be used in stoichiometric quantity or phosgene may be used in excess. If the reaction is carried out in an aqueous phase, an inert organic solvent such as cyclohexane, benzene, toluene, xylene, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, ethylene chloride, diethylether or diisopropylether may be added.

As will be seen from the following examples, the vulcanization accelerators according to the invention are distinguished by their high resistance to premature vulcanization. They achieve a high vulcanization rate and excellent mechanical properties in the vulcanizates, in particular a low compression set (in accordance with DIN 53,517) and high tension values, tear resistances, elasticity and hardness. In particular, they do not cause blooming or matting of the surface of the vulcanizates. The compounds which have more than 3 carbon atoms in the alkyl radicals are practically odourless and do not impart an odour to the vulcanizates.

The vulcanization process according to the invention will be explained in the following examples. The test methods used are summarized in Table l.

thiuramic monosulphide as accelerators, which also does not give rise to blooming, the advantages of S,S'-carbonyl-bis-dialkyldithiophosphates as regards vulcanization rate and the mechanical properties obtained, especially the compression set, become very clear.

2-mercaptobenzothiazole Tetramethyl-thiuramic monosulphrde 5 Mixture No.-

1: 8,8 carbonyl bis dimethyl dithiophos- Parts by Wei ght 0.5 0.4

EXAMPLE 2 phate 2: S,S'-carbonyl-bls-d1ethyld1th1ophosphate 1.2 The following EPDM rubber mixture was prepared in 31 y bls l-P PY P 1 2 an internal mixer in the usual manner: 10 Phat? "7"":

, 4: 8,8 -carbonyl bis di-lsopropyl-dlthiophos- Parts by welght phate 12 A vulcanizing type Of contalning 5: S,S'.carbonyl (2..methoxyethyl)- ethylidene norbornene as diene component (Keldithiophosphate 1.2 tan 512) 100.0 15 6: 8,5 carbonyl bis dl-n-butyl dithiophos- A furnace black which improves the extrudability phate 1 1.2 ofth mixture (FEF carbon black, Corax A) 60.0 Zmc dlethyl h r m An aliphatic mineral 011 (Ingraplast NS) 20.0 81 Wflhout addltlve ZlnX Stepwise heating at 120 C., 150 C. and 170 C. was Steanc acid -1 20 carried out with the above mixtures and the following Sulphur 1.5 data were obtained:

TABLE 3 Mixture number 1 2 3 4 FDM,M,HEFDM,M,HEFDM,M,HEFDM,M,HE 200 300 00 300 200 300 200 300 fimlnutes at 120 C; 10 230 49 10113111111185 at 120 C 10 290 50 minutes at 120 C- 10 552 49 minutes at 120 C. 10 550 49 minutes at 120 C. 690 51 minutes at 120 C. 113 730 51 GOminutes at 120 C. 140 720 52 75 minutes at 120 C. 140 630 52 9011111111599 at 120 C. 145 540 53 5minutesat150 O- 25 540 5 10 minutes at 150 C- 140 750 51 51 15 minutes at 150 C. 160 640 51 53 20 minutes at 150 C. 160 550 51 53 30 minutes at 150 C. 155 490 53 54 45 minutes at 150 C- 155 420 54 54 minutes at 150 C- 150 390 54 54 minutes at 150 C- 155 390 52 54 minutes at 150 C- 155 390 71 54 54 Bmjnutes at 170C 160 620 44 51 54 10 minutes at 170 C. 155 460 52 54 15 minutes at 170C 160 470 69 52 54 Scorch time at 120 0, (mm) 38 Maximum modulus at 200% elongation at 150 C. (limiting value 90/150 0., kg. wtlomfi)--- 97 91 Blooming None None None None Compression set (percent):

TABLE 3Conti.nued

Mixture number 5 6 7 3 FDM,M,HEFDM,M,HEFDM,M,HEFDM,M,HE 200 300 200 300 200 300 200 300 5minutesat120C 10 170 37 50 5 190 33 43 5 130 4 33 43 10 130 35 50 10111151115551: 120C 10 460 3 7 45 51 10 230 4 37 43 30 650 12 29 45 49 10 140 39 5o 15 minutes at 120C--- 35 660 16 22 53 51 10 460 6 6 44 43 35 720 30 43 54 49 10 320 6 5 45 50 20minutesat120 C--. 90 770 25 39 53 51 35 630 14 19 51 50 95 510 43 63 53 49 25 620 13 17 52 51 30minutesat120 C..- 140 750 35 56 62 53 720 23 45 60 51 470 54 31 61 50 95 320 24 33 53 51 45 minutes at 120 C--. 155 590 43 76 65 53 540 46 71 65 53 460 62 94 63 50 150 700 40 63 64 52 60 minutes at 120C 155 530 56 36 66 54 130 460 53 33 67 53 410 69 97 65 51 155 630 47 72 65 53 7511111111105 at 120C 155 470 63 95 63 54 125 400 64 95 69 54 135 390 72 39 65 52 150 560 59 32 67 54 90 minutes at 120C 150 410 72 103 69 54 120 330 74 109 70 54 130 350 74 101 66 53 460 60 91 68 54 fiminutes 51; C 130 300 30 49 59 51 65 670 19 30 54 51 110 610 23 34 53 51 60 699 20 30 55 51 lominutesat 150C 160 570 54 35 65 53 145 570 47 74 65 52 130 550 63 30 66 52 160 700 42 67 64 51 15 minutes at 150C 150 420 66 101 68 54 145 430 67 100 63 54 135 430 68 37 67 53 150 500 53 39 67 53 2011111111555 at 150C 400 74 114 63 54 135 360 73 111 69 54 135 420 74 94 68 54 150 450 64 93 68 54 30 minutes at 150C 145 360 32 129 70 54 135 320 32 127 70 54 140 350 30 110 69 54 150 400 72 109 70 53 4511111111555 at; 150C 90 143 70 54 135 230 90 70 54 140 320 33 123 69 54 150 350 30 127 71 54 60mjnutesat1600 94 71 56 145 230 96 71 55 145 270 37 70 54 145 330 33 132 71 54 75 minute at 150C 95 71 56 130 260 95 71 54 130 260 39 7o 54 140 300 37 71 54 9011111111155 at 150C 94 143 72 55 135 270 96 72 54 130 270 90 70 54 140 310 34 132 71 54 5511511165 at 170C 63 107 67 54 135 400 66 101 67 52 140 410 69 102 63 51 530 53 90 66 51 1.011111111139881; C 155 350 34 136 69 54 140 330 31 131 69 54 135 340 79 125 63 53 155 400 72 155 69 53 lfiminutes at 170C 150 330 35 137 69 54 135 290 3669 135 330 79 69 54 155 330 77 125 69 54 Scorch time at 120 C. (min.) 19. 5 26. 5 30 Maximum modulus at 200% elongation at 150 C. (limiting value 90/150 0., kg. WtJcmfl) 95 '90 87 Blooming None None Severe None Compression set (percent):

22 h. 70 C 3.0 3.0 10.2 11.3 70 1i. 100 C 50. 2 49. 2 65. 3 67. 3

9 EXAMPLE 3 The following mixture was prepared in an internal mixer in the. usual manner:

Parts by weight 10 The following compounds were synthesized in analogous manner:

S,S-carbonyl-bis-di-methyl-dithiophosphate; u 1.5438 C H O P S (311.4): Calc. (percent): C, 19.3; H, 3.39.

1117 g. (15.5 mol) of n-butanol are added dropwise 50 to 860 g. (3.87 mol) of phosphorus pentasulphide at 20 C. (cooling with water) with stirring. Stirring is then continued at 50 C. until the evolution of hydrogen sulphide has ceased. The reaction mixture is cooled to room temperature, degasified under vacuum and filtered. 1775 g. of dibutyldithiophosphoric acid (97% of the theory) are obtained.

820 g. (3.1 mol) of sodium-di-n-butyl dithiophosphate which can be prepared by treating dibutyldithiophosphoric acid with aqueous sodium hydroxide solution in the usual manner are reacted with 153.5 g. (1.55 mol) of phosgene in 1.6 l. of water at 5 C. to C. Stirring is continued for 2 hours at 0 C. and the reaction fixture is then made slightly alkaline and extracted by shaking it 3 times with methylene chloride. The combined methylene chloride solutions are washed with water, dried over sodium sulphate and evaporated under vacuum. 803 g. of a pale yellow oil, amounting to 100% of the theory (based on the amount of sodium dibutyldithiophosphate put into the reaction) of S,S-carbonyl-bis-di-n-butyldithiophosphate are obtained;

77 1.5265. C H O P S (510.7): Calc. (percent): C, 40.0; H, 7.1;

O, 15.7; P, 12.1; S, 25.1. Found (percent): C, 39.8; H,

7.2; O, 16.5; P, 12.1; S, 24.5.

A slowly vulcanizing type of EPDM containing di- 5 Found (percent): C 19.7; H, 4.6.

gg ggifi as Ilene (Kil 1000 S,S-carbonyl-bis-diethyl-dithiophosphate; 1.5249 A furnace black which improves the extrudability 091-1200513254 (398-5): Calc- (P t): C, 27.1; H, 5.1.

of the mixture (Corax A, FEF carbon black) 60.0 f? g. Analiphafic and oil ungraplast NS) 20D S,S-c ar onyl-bisi-isopropyl-dithiophosphate, M.P. 82- Zinc oxide 5.0 83 C:

Stearic acid 1.0 C13H2805P2S4 1 Sulphur 1 5 S,S'-carbonyl-bis-di-n-propyl-dithiophosphate; 71 1.5239

ZQmercaptobenzothjazole 0 5 C13H28O5PZS4 Cale (p C H,

Tetramethyl thiuram monosulphide 0.4 15 ffound (Perc em)f 34-0;

niphenylthiourea L0 S,S ;:r r;ny/lib1s-d1-(2 methoxyethyl) dithlophosphate;

The accelerators were then mixed on a mill (parts by k C H O P S (518.6): Calc. (percent): C, 30.1; H, 5.4. weight based on 100.0 parts by weight of rubber). Found (percent): C, 30.2; H

MIXtIlIIE B S,S'-carbonyl-bisdi-n-pentyl-dithiosphosphate; 77 1.5173 g; -Z Y -g dlthwphosphate 0 1 1 05 5, (566.8): c515. (percent): 0, 44.5; H, 7.8.

' m e Y 10091 amate Found (percent): C, 45.2; H, 81.1.

Stepwise vulcanization was carried out at 120 C. and Y Y P P "12 1-4961 15010. with the above mixtures and the following data 25 5z 5 2 4 Calc- (P were obtained: Found (percent): C, 49.2; H, 9.3.

TABLE 4 Mixture number M M M M FD200800HEFD200300HE Sminutes at 120C 10 220 4 4s 10 200 5 a7 47 IOminutesat 120C--- 15 710 9 10 4s 25 680 24 55 45 45 20111111111555: 120C-.. 550 15 25 52 4s 75 750 so 42 4s 4s 30minutesat1200 115 550 25 as 48 100 750 55 4s 50 48 4511111111555 at 120C--- 155 s00 31 5o 59 42 1:15 700 40 55 5a 49 minutesat120 155 550 42 555 51 50 150 550 44 5o 59 50 76minutesat120C- 170 510 4a 5a 51 150 550 45 75 51 50 9011111111155 at 120C- 155 555 50 77 54 51 150 529 49 75 52 5o 5m1nu17es at 150 0... 124 590 24 40 55 4a 120 700 34 49 5s 45 1011111111555 at 150C.--

170 720 59 52 50 48 150 570 42 57 59 49 15 minutes at 150C- 170 590 49 77 52 49 155 510 47 54 5o 50 20min11tesat150 o- 150 510 55 87 55 51 155 550 51 7a 52 50 30minutes at 150C- 150 520 50 52 51 150 520 5o 25 52 51 45 minutesat 159 150 550 77 121 55 51 150 450 72 55 51 60minutesat1500- 155 550 79 127 59 5a 150 410 75 111 55 52 75 minutes at1500 150 520 55 137 59 55 150+390 79 57 52 00m1nutesat150C 150 540 87 140 70 55 380 81 135 58 52 Scorch timeat 120 0. (min.) 23 12 Maximum modulus at 200% elongation at 150 C. (limiting value 907150 0. kg. wt./em.) s7 s1 Blooming None Severe EXAMPLE 4 S,S'-carbonyl-bis-di-isobutyl-dithiophosphate; r1 1.5203

C17H36O5P3S4 (510.7): Calc. (percent): C, 40.0; H, 7.1.

Found (percent): C, 40.4; H, 7.2.

When using an alcoholic mixture of 50 percent by weight of n-butanol and 50 percent by weight of isobutanol, a product which has the following data is obtained:

C H O P S (510.7): Calc. (percent): C, 40.0; H, 7.1.

Found (percent): C, 39.8; H, 7.2. n 1.5258

When an alcoholic mixture of 50% by weight of nbutanol and 50 percent by weight of n-pentanol is used, a reaction product which has the following overall composition is obtained:

C H O P S (538.7): Calc. (percent): C, 42.4; H, 7.47.

Found (percent): C, 52.5; H, 7.6. 77 1.5222

What is claimed is:

1. In the process of vulcanizing an ethylene-propylene terpolymer in which the vulcanizantion is effected in the presence of sulphur or a sulphur donor, the improvement which comprises employing as vulcanization accelerator (a) a compound of the formula 1 1 wherein each R is alkyl having 1 to 6 carbon atoms or alkoxyalkyl having 1 to 4 carbon atoms in the alkoxy moiety and 1 to 6 carbon atoms in the alkyl moiety and (b) a thiazole accelerator.

2. The process of claim 1 wherein (b) is Z-mercaptobenzothiazole, dibenzothiazyl disulphide or the zinc salt of Z-mercaptobenzothiazole.

3. The process of claim 2 wherein said vulcanization accelerator contains, based on the weight of said terpolymer, 0.1 to 5.0% by weight of (a) and 0.2 to 2.0% by weight of (b).

4. The process of claim 3 wherein said vulcanization accelerator also contains up to 2.0% by weight of (c) tetrarnethylthiuram disulphide, tetraethylthiuram disulphide, tetramethylthiuramic monosulphide or 'dimethyldiphenylthiuramic disulphide and up to 2.0% by weight of (d) a thiourea.

12 5. The process of claim 4 wherein (a) is S,S'-carbonylbis-di-n-butyl dithiophosphate ,(b) is 2-mercaptobenzothiazole, (c) is tetramethylthiuram monosulphide and (d) is diphenylthiourea.

References Cited UNITED STATES PATENTS 3,419,521 12/1968 Scott 260-415 3,629,210 12/1971 Apotheker 26079.5

JOSEPH L. SCHOFER, Primary Examiner C. A. HENDERSON, JR., Assistant Examiner US. 01. X. R. 2s2 1s2; 260-783, 785 

